<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
      /*  输入框的布局*/
        .InputAddOn {
            display: flex;
        }

        .InputAddOn-field {
            flex: 1;
        }
    </style>
</head>
<body>
<div class="InputAddOn">
    <span class="InputAddOn-item">InputAddOn-item</span>
    <input class="InputAddOn-field">
    <button class="InputAddOn-item">InputAddOn-item</button>
</div>
</body>
</html>